Objective:To study the essence of the cytotoxicity of T activated killer (T AK) cells costimulated by anti CD3 monoclonal antibody (CD3McAb) and recombinant interleukin 2 (rIL 2).Methods:T AK activity against leukemia cells (K 562 cells and Raji cells) were determined separately in a MTT assay.Results:The cytotoxicity of T AK cells were composed of mainly four parts:CD3 McAb activated CD3AK activity(50%),rIL 2 induced LAK activity(30%),NK activity(10%) and the activities of inhibitory factors...